Individuals with CF with an identified mutation in the cystic fibrosis transmembrance regulator (CFTR) (i.e., any of the known variants of the CFTR gene, such as the change in F508 allele) who are between the ages of 18 years to 65 years will be included in the apheresis portion of the study. Patients will have been or will be genotyped under another protocol. Patients must be colonized or have a history of colonization with P. aeruginosa. Patients may have cultured other organisms (e.g., Burkholderia cepacia).